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[Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation |
Date: |
Mon, 23 Jan 2012 19:38:30 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Forking an expr process for every byte of the input data slows down the
checksum calculation massively. Fix this while still remaining portable
by implementing the algorithm in awk.
Signed-off-by: Jan Kiszka <address@hidden>
---
That "remaining portable" is an unproven claim. So please check that
problematic NetBSD and also mingw. Thanks!
scripts/signrom.sh | 18 ++++++++----------
1 files changed, 8 insertions(+), 10 deletions(-)
diff --git a/scripts/signrom.sh b/scripts/signrom.sh
index 9dc5c63..f0f460e 100755
--- a/scripts/signrom.sh
+++ b/scripts/signrom.sh
@@ -23,22 +23,20 @@
# did we get proper arguments?
test "$1" -a "$2" || exit 1
-sum=0
-
# find out the file size
x=`dd if="$1" bs=1 count=1 skip=2 2>/dev/null | od -t u1 -A n`
-#size=`expr $x \* 512 - 1`
size=$(( $x * 512 - 1 ))
# now get the checksum
nums=`od -A n -t u1 -v -N $size "$1"`
-for i in ${nums}; do
- # add each byte's value to sum
- sum=`expr \( $sum + $i \) % 256`
-done
-
-sum=$(( (256 - $sum) % 256 ))
-sum_octal=$( printf "%o" $sum )
+sum_octal=`echo $nums | awk 'BEGIN {
+ getline data_str;
+ sum = 0;
+ n = split(data_str, data, " ");
+ for (i = 1; i <= n; i++)
+ sum = ( sum + data[i] ) % 256;
+ printf "%o", (256 - sum) % 256;
+}'`
# and write the output file
cp "$1" "$2"
--
1.7.3.4
- [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation,
Jan Kiszka <=
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Stefan Weil, 2012/01/23
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Jan Kiszka, 2012/01/23
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Stefan Weil, 2012/01/23
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Anthony Liguori, 2012/01/23
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Jan Kiszka, 2012/01/23
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Anthony Liguori, 2012/01/23
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Stefan Weil, 2012/01/23
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Andreas Färber, 2012/01/24
- Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Paolo Bonzini, 2012/01/24
Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation, Christoph Egger, 2012/01/24